Formation of 1D and 2D gold nanoparticle arrays by divalent DNA-gold nanoparticle conjugates

Divalent DNA-AuNP (gold nanoparticle) conjugates comprising two DNA strands at diametrically opposed positions are prepared. Highly linear 1D and tetragonal lattice-like 2D AuNP arrays are constructed using the conjugates and DNA assemblies based on T- and double-crossover motifs and the Holliday junction.     

Secondary electron emission in scanning Ga ion, He ion and electron microscopes

The secondary electron (SE) emission for Ga ion, He ion and electron impact have been calculated using Monte-Carlo simulations, in which the trajectories of all the collision partners (i.e., primary ions, recoiled target atoms, and excited electrons (electron cascade) along which SEs are excited) have been simulated. The SE yields for Ga ion impact show a gradual decrease with increasing Z₂ which is opposite to that found for electron impact. The main reasons for the decrease in SE yield for Ga are the decrease in number and energy of electrons excited by the primary ions and the decrease in contribution of the recoiled atoms to the SE yield with increasing Z₂. For electron impact, both primary electrons and backscattered electrons (BSEs) excite the SEs. The additional SE excitation created by the electron cascade by BSEs is enhanced for high-Z₂ metals especially at E > a few keV. For He ion impact, the Z₂-dependence is between that for the Ga ions and the electrons and is weak because the He ion is light but still much heavier than an electron. As to the lateral resolution, the electron excitations by trapped He ions dominate the SE yield, so that the SE excitation volume is narrower than for electron and Ga impacts. This small contribution of BS He ions to the SE yield does not increase the information depth determined by the trapped He ions, in contrast with the large contribution of BSEs to the SE yields for SEM imaging. The simulated incident-angle dependence in SE yields shows that the topography contrast for He-SIM imaging is clearer than that obtained by SEM and Ga-SIM imaging.     

聚丙烯酸/聚砜交联复合膜的反渗透分离性能的研究Ⅱ.对有机醇、胺、醛、酸水溶液的分离规律

研究了聚丙烯酸／聚砜交联复合膜对有机醇,胺,醛,酸水溶液的反渗透分离规律,对于有机醇水溶液,还应用Spiegler-Kedem膜输送方程对实验数据进行了解析,得到了反射系数σ,溶剂水渗透系数Lp和溶质渗透系数ω等膜参数。     

Effect of electro-chemical properties of sodium salts of various anions on their diffusional parameters in symmetrical cellulose acetate membranes

A relation was obtained between electro-chemical properties of sodium salts (NaCl, NaBr, and Na₂SO₄), and the thermodynamic property of permeability in symmetrical cellulose acetate membranes, the distribution coefficient K and the kinetic property, the overall diffusion coefficients D. K and D were obtained by the method we proposed using measured unsteady- and steady-state dialysis data. The K values increase with the increase of water content and are in the range of 10⁻² for sodium halides and 10⁻³ for Na₂SO₄. D is found to increase with the increase of the solute concentration, and the extrapolated values of D to zero concentration D⁽⁰⁾ are obtained as 0.015–0.03 μm²/s and increase with the increase of water content in the membrane. D can be divided into the concentration independent diffusion coefficients in the dense part of the membrane D_d and in the porous D_p, applying a two-part (perfect or dense and imperfect or porous) model of the membrane. Contrary to D_d, D_p increases with the increase of W_w and can be correlated as D_p,c = _d exp (γ × W_w). It is shown that the averaged D_d, _D increases with the increase of the quantity of the ionic mobility u of the solutes at infinite dilution divided by valence, and that the parameter γ increases with the increase of the ionic mobility u. The value of K increases slightly with the increase of water content and decreases with the increase of the Flory—Huggins parameter χ. The Flory—Huggins parameter χ is calculated from the measured values of distribution coefficients and data obtained from the literature. And it was found that the gradient of linear decrease of χ (λ_cation) depends on equivalent ionic conductivity of anion of salt, λ_an.     

Adaptation study for biofilm of the urinary tract via highly complicated bladder model (biofilm model of the urinary tract)--experimental study using automatic simulator of the urinary antimicrobial agent concentration

With the view of making an adaptation study for biofilm of the urinary tract, we devised a computer-controlled highly complicated bladder model (biofilm model of the urinary tract) that allowed the simulation of time-course changes in the urinary concentration of antimicrobial agents. Clarithromycin (CAM), which is reported to have an anti-biofilm action, was examined at urinary levels approximating clinical concentrations and its effect on biofilm was determined. The following results were obtained. 1) Ofloxacin (OFLX, 200 mg x 2/day, MIC; 8 micrograms/ml), which is active against Pseudomonas aruginosa, caused apparent microbial elimination from the model at 42 hours, but bacterial regrowth occurred 4 hours after withdrawal of this agent. No disappearance of the biofilm was noted with OFLX suggesting that this was the cause of bacterial regrowth. 2) The combination of OFLX (200 mg x 2/day) and CAM (MIC; > 128 micrograms/ml, 200 mg x 2/day) on anti-biofilm agent, with no effect on P. aeruginosa, eliminated bacteria from the bladder model more rapidly and prolonged the regrowth time to 10 hours after withdrawal of the antimicrobial agents. Disappearance of most of the biofilm and only slight microbial adhesion was noted. 3) The combination of OFLX (200 mg x 2/day) and CAM (400 mg x 3/day) caused microbial elimination from the bladder model with no regrowth at 30 hours after withdrawal of the antimicrobial agents. The biofilm disappeared completely and no microbial adhesion was noted. 4) CAM alone (400 mg x 3/day) allowed microbial recovery to the initial level within 48 hours after withdrawal, but led to disappearance of the biofilm and the adhesion of microbes without a glycocalyx. 5) These results suggest that the anti-biofilm action of CAM is dose-dependent, and that combined use of an appropriate antimicrobial agent and anti-biofilm agent like CAM may be effective for biofilm infections of the urinary tract.     

Hydrophilic membranes for pervaporation: An analytical review

An analytical review has been attempted on the issues encountered in selecting polymers for hydrophilic pervaporation (PV) membranes. It is well known that permselectivity is determined by selective sorption and by selective diffusion. Selective sorption is governed by the presence of the active centers in the polymer which are capable of specific interactions with water. The analysis of the influences of the type of interactions of water-active centers of the polymer on the membrane performances are presented. Selective diffusion is governed by the rigidity and the regularity of the polymer structure and also by the constructure of the polymer's interspace. There is a net of bonds and crosslinks in the polymer due to existence of inter- and intramolecular interactions in it. This net is responsible for the stability of the mass transfer properties of the polymer to the feed water. The influences of the degree of swelling and frequencies of the crosslinks in the polymer are analysed. The main role of the selective diffusion in the selective permeation is demonstrated. The possibility of the existence of two different channels (hydrophilic and hydrophobic) for the permeation of water and organics is discussed, and it has been concluded that there are two different channels for friable polymers which have fragments with not so strong inter- and intra-molecular interactions. But in the polymers with strong inter- and intra-molecular interactions and a narrow net of these bonds (e.g., polyelectrolyte complexes), the hydrophobic channels are strongly collapsed. They can be opened only by water at its high feed concentrations. It was concluded that one of the most prospective ways to create highly permeative and highly selective materials for dehydration of organics by PV is using polyelectrolyte complexes (especially for the separation of water with organic molecules, which have more than three carbon atoms in total).     

Theory of spectral linewidth of external cavity semiconductor lasers

A new formula of the spectral linewidth of external cavity semiconductor lasers is proposed, with which linewidth narrowing with the optical feedback is discussed. It is shown that in the limit of large external cavity length, the linewidth caused by the phase diffusion due to spontaneously emitted photons becomes dominant and the linewidth decreases proportionally to the inverse of the external cavity length.     

醋酸纤维素衍生物反渗透膜对低分子量有机物分离特性研究

研究用醋酸纤维素衍生物氰乙基醋酸纤维素、羟丙基醋酸纤维素和醋酸纤维素反渗透膜对有机醇、有机酸及有机胺类水溶液的分离特性,考察操作压力对反渗透分离特性的影响,并应用不可逆热力学过程得出的Spiegler—Kedem膜输送方程解析实验数据,获得了反射系数σ、溶质渗透系数ω和溶剂水渗透系L_p等膜参数。